Effect of Contact LensWear on the Diurnal Profile of Matrix Metalloproteinase 9 in Tears

Purpose. This study set out to determine how contact lens wear affects the profile of matrix metalloproteinase 9 (MMP-9) in the tear film. Methods. Flush tears were collected from 47 healthy neophytes before lens wear, during the first day of lens wear, and after 1 month adaptation. Participants were randomized to either Acuvue Oasys or O2OPTIX with the choice of extended (EW) or daily wear (DW). Each time, tears were collected at midday, before sleep, and on waking and analyzed for concentrations of total protein, MMP-9, and its regulators TIMP-1 (tissue inhibitor of metalloproteinases 1) and NGAL (neutrophil gelatinase-associated lipocalin). Results. Initial extended contact lens wear resulted in significantly elevated MMP-9 levels on waking (3598.7 +/- 3229.1 ng/mL) compared with the same time point at baseline (2123.3 +/- 1762.8; p = 0.02), whereas DW remained unchanged (2373.0 +/- 2091.6 ng/mL; p = 0.61). After 1 month of EW, the levels on awakening were no longer different to those of baseline (2408.2 +/- 1376.1 ng/mL; p = 0.63). The MMP: TIMP ratio during EW was greater after the first night (18.6 +/- 19.9) than both no wear (13.2 +/- 13.4) and 1 month (10.4 +/- 7.7), but only the latter was significant (p = 0.048). The profile of NGAL did not differ from baseline (p = 0.055). Conclusions. In the neophyte, the initial period of overnight lens wear seems to disturb the tear film homeostasis, as indicated by a significant increase in MMP-9 on awakening. The return to baseline by 1 month suggests that an adaptive process takes place. No comparable changes are seen in DW. (Optom Vis Sci 2013; 90: 419-429)